When Nara tried this he didn't use an actual modpack, since there were none out for 1.6 and I wanted to play 1.6. However, Mat's using a modpack, so you literally just need to download the launcher and the pack, and join the server.
It also doesn't matter what version forge is in, because if the mods aren't updated, then it won't work.
By the way, just for the public, I'm interested. =P